1. Field of the Invention
This invention relates to semiconductor device packaging teleology, and more, particularly, to a method of fabricating a semiconductor device package of the typo having a core-hollow portion that is typically used to house an optically-sensitive semiconductor device, such as an image sensor or a,n ultraviolet-sensitive EPROM (Electrically-Programmable Read-Only Memory) device, which can help prevent resin flash on a lead frame during the molding of the core-hollowed portion.
2. Description of Related Art
Semiconductor device packaging technology is used to pack one or more semiconductor chips in a single module that can be easily handled and mounted onto printed circuit boards. Typically, the semiconductor chip or chips are enclosed inside an opaque compound (or called an encapsulated body), and is thus invisible from the outside. IIowever, for optically-sensitive types of semiconductor chips, such as image-sensor chips or ultraviolet-sensitive EP-ROM (Electrically-Programmable Read-Only Memory) chips, it is required to allow these chips to sense ambient light. For this reason, a special package configuration is used to pack these types of semiconductor chips. One conventional package configuration to pack an optically-sensitive semiconductor chip is to mount it in an encapsulated body having a core-hollowed portion; and then, after performing wire bonding to the chip, hermetically seal a transparent lid over the opening of the core-hollowed portion of the encapsulated body. Ambient light can then pass through the transparent lid to the inside of the encapsulated body to be sensed by the chip enclosed therein.
One drawback to the foregoing package configuration, however, is that, during the molding of the core-hollowed portion, resin flash on a lead frame is a serious problem, which would undesirably degrade the quality of the die attachment and wire bonding on the flashed parts of the lead frame. To solve this problem, various solutions have been proposed, including, for example, the U.S. Pat. No. 5,070,041 entitled xe2x80x9cMETHOD OF REMOVING FLASH FROM A SEMICONDUCTOR LEADFRAME USING COATED LEADFRAME AND SOLVENTxe2x80x9d issued on Dec. 3, 1991, which can remove resin flash built up on the lead frame without damaging a resin molded section. This patented method is characterized in the steps of coating an organic high-molecule substance over the areas of the lead frame that are to be uncovered by the molded compound; and then, after the encapsulated body is completely formed, using a special solvent to wash away the organic high-molecule coating, whereby the resin flash can be removed together with the organic high-molecule coating. After this, a semiconductor chip is mounted onto the flash-free die pad, and then a transparent lid is hermetically sealed to the opening of the core-hollowed portion of the encapsulated body.
The foregoing patented method, however, has the following drawbacks. Firstly, the step of coating the organic high-molecule substance and the subsequent step of dissolving the coating to remove resin flash are quite complex in procedure and costly to implement, making the overall fabrication process quite cost-ineffective. Secondly, the solvent can be corrosive to the lead frame, which would also undesirably degrade the quality of the die attachment and wire bonding on the lead frame. Third, the solvent, after being used, would cause pollution and thus is environmentally-unfriendly to use.
It is therefore an objective of this invention to provide a new method for fabricating a semiconductor device package of the type having a core-hollowed portion, which can help prevent resin flash on lead frame during the molding of the core-hollowed portion.
It is another objective of this invention to provide a new method for fabricating a semiconductor device package of the type having a core-hollowed compound, which can help prevent resin flash on a lead frame without having to use an expensive coating process and environmentally-pollutant solvent.
It is still another objective of this invention to provide a new method for fabricating a semiconductor device package of the type having a core-hollowed compound, which can help prevent resin flash on lead frame in a more cost-effective and quality-assured way than the prior art.
It is still another objective of this invention to provide a new method for fabricating a semiconductor device package of the type having a core-hollowed compound, which allows the fabricated package to be more reliable to use than the prior art.
In accordance with the foregoing and other objectives, the invention proposes a new method for fabricating a semiconductor device package of the type having a core-hollowed compound. The method of the invention includes the following procedural steps: (1) preparing a lead frame having a die-pad portion and a finger portion; (2) preparing an electrically-insulative support pillar having a flat top surface, and which is dimensioned to a predetermined width and a predetermined height; (3) preparing a molding tool set including a top inserted mold and a bottom cavity mold; wherein the top inserted mold is formed with a sidewall cavity structure, while the bottom cavity mold is formed with a base cavity structure whose depth is substantially equal to the height of the support pillar; (4) containing the support pillar within the base cavity structure of the bottom cavity mold; and then, placing the lead frame over the support pillar, with the die-pad portion and the inner end of the finger portion of tho lead frame being placed directly over the top surface of the support pillar; (5) pressing the top inserted mold down against the lead frame, allowing the entire die-pad portion and the inner end of the finger portion of the lead frame to be substantially airtightly clamped between the support pillar and the top inserted mold; (6) performing a molding process to fill a molding material into the sidewall cavity structure of the top inserted mold and the remaining void space of the base cavity structure of the bottom cavity mold that is unoccupied by the support pillar, so as to form an encapsulated body having a top sidewall part defining a core-hollowed portion for die attachment and wire bonding and a bottom base part encapsulating the support pillar; (7) removing the top inserted mold and the bottom cavity mold; (8) performing a die-attachment process to attach at least one semiconductor chip onto the die-pad portion of the lead frame within the core-hollowed portion of the encapsulated body; (9) performing a wire-bonding process to connect a set of bonding wires for electrically coupling the semiconductor chip to the inner cad of the finger portion of the lead frame; and (10) performing a lidding process to hermetically seal a lid over the opening of the core-hollowed portion of the top sidewall part of the encapsulated body.
The foregoing method of the invention is characterized in the use of the support pillar, which is positioned beneath the lead frame when the lead frame is clamped between a top inserted mold and a bottom cavity mold during the molding process, to help prevent resin flash on the lead frame during the molding of the core-hollowed portion. As a result, the method of the invention can help strengthen the bonding of the semiconductor chip on the die pad as well as the bonding of wires on the inner end of the finger portion of the lead frame, making the overall package body more assured in quality and reliability.